JP4355858B2 - Antenna structure - Google Patents

Description

  The present invention relates to an antenna structure in a wireless communication device such as a mobile phone.

  2. Description of the Related Art In mobile communication devices, particularly portable telephones, antenna devices configured to be stretchable by combining linear elements and spiral elements with antenna elements are widely used in consideration of portability.

  Recently, in order to provide location information services, it is necessary to configure an antenna that can use two different frequency bands for communication and service provision, and can effectively use the frequency band of radio waves. ing.

In order to be able to use two frequency bands, there is an antenna structure in which a matching circuit that resonates in two different frequency bands is disposed between an antenna element and a feed line (see, for example, Patent Document 1).
JP 2001-185936 A

  However, in a conventional antenna structure using a matching circuit, a plurality of frequency bands can be used with one antenna, so that the matching circuit becomes complicated. Further, since the antenna circuit is composed of small components, the bandwidth of the entire antenna circuit is narrowed, resulting in a large impedance deviation and an increase in mismatch loss.

  Furthermore, as the use frequency increases, the case length cannot be ignored with respect to the wavelength, and the directivity pattern deteriorates due to the influence of current generated on the case side.

  An object of the present invention is to provide a wideband antenna structure capable of communicating in a plurality of frequency bands without requiring a complicated matching circuit.

In order to solve the above-described problems, the invention described in claim 1 is an antenna structure, and for example, as shown in FIGS. 1 to 6, 1 / of the wavelength λ1 of the center frequency f1 of the first use frequency band. A first antenna (extensible antenna 20) having an electrical length of 4 and having a first hot part at one end, and a notch (notch 31) extending from one end toward the other end, and the end divided into two by this notch A second antenna (notch antenna 30) having a second hot part in one of the parts and a ground part in the other, the notch being an electrical length of ¼ of the wavelength λ2 of the center frequency f2 of the second use frequency band and Ri Do because, from said one end of the second antenna to the other has an electrical length of a quarter of the wavelength λ1 of the center frequency f1 of the first usable frequency band, the first antenna and the second antenna Are arranged to extend in opposite directions, By fed simultaneously from the unbalanced feed line for passing, it constitutes an asymmetric dipole antenna having an electrical length of 1/2 wavelength .lambda.1, characterized in that.

The invention according to claim 2 is the antenna structure according to claim 1 , wherein the center frequency f2 of the second use frequency band is an even multiple of the center frequency f1 of the first use frequency band. Features.

According to a third aspect of the invention, an antenna structure according to claim 1 or 2, wherein the second antenna is a tubular conductor (notch pipe 32), the two places spaced in the circumferential direction of the end It has two notches (notches 33 and 34) provided in the axial direction, and one notch (notch 33) has an electrical length of ¼ of the wavelength λ2 of the center frequency f2 of the second use frequency band. The other notch (notch 34) has an electrical length that is ¼ of the wavelength λ2 ′ of the frequency f2 ′ different from the center frequency f2 of the second use frequency band . The second hot part is provided on one side, and the ground part is provided on the other side .

Invention of Claim 4 is an antenna structure as described in any one of Claims 1-3 , Comprising: The said 2nd antenna is a tubular conductor (notch pipe 32), The said 1st antenna is included in this inside. One antenna (linear element 21) is accommodated.

Invention of Claim 5 is the antenna structure as described in any one of Claims 1-4 , Comprising: The said 2nd antenna is formed by giving metal plating in a housing | casing (back housing | casing 12). It is characterized by.

  According to the present invention, it is possible to communicate in two different frequency bands by the antenna structure including the first antenna corresponding to the first use frequency band and the second antenna corresponding to the second use frequency band. Become.

  In addition, since the first antenna and the second antenna have an electrical length that is ¼ of the wavelength λ1 of the center frequency f1 of the first use frequency band, and extend in the opposite direction from the conductive power feeding portion, An asymmetric dipole antenna having an electrical length ½ of the wavelength λ1 of the center frequency f1 of the first use frequency band is configured to improve the radiation efficiency in the first use frequency band of the antenna and enable stable communication. become.

  Further, the second antenna has a tubular shape, and is cut at an electrical length of ¼ of the wavelength λ2 and at a frequency f2 ′ different from the center frequency f2 of the second used frequency band at two locations spaced in the circumferential direction at one end. A notch antenna 30 with respect to the frequencies f2 and f2 ′ is formed by providing a cut of an electrical length of ¼ of the wavelength λ2 ′, and a wide band can be achieved with respect to the second frequency band.

  Hereinafter, a first embodiment of the present invention will be described in detail. 1A and 1B are diagrams of a mobile phone 10 to which the antenna structure of the present embodiment is applied. FIG. 1A is a front view, FIG. 1B is a side view, and FIG. As shown in FIG. 1A, the mobile phone 10 is configured by combining a front housing 11 and a back housing 12. In the front housing 11, a receiver 14, a display device 15, an input device 16, a transmitter 17, and the like are arranged in order from the upper end to the lower end. In addition, as shown in FIG. 1B, the mobile phone 10 incorporates a high-frequency circuit 18 substrate, a battery 19 and the like.

The antenna structure of the present invention is built in the rear housing 12 and is composed of an extendable antenna 20, a notch antenna 30, and a coaxial cable 40.
The telescopic antenna 20 includes a linear element 21 and a spiral element 22 disposed at the upper end portion of the linear element 21. FIG. 1 shows the telescopic antenna 20 when it is extended. At the time of extension, the linear element 21 is fixed to the fixing bracket 13 provided on the upper portion of the rear housing 12 at the lower end thereof, and is connected so as to be electrically conductive. This connection portion becomes a power feeding portion of the telescopic antenna 20. The linear element 21 is accommodated in the guide pipe 23 when not in use. The guide pipe 23 is provided inside the rear housing 12 with the vertical direction as the axial direction.

  When the linear element 21 is used, the spiral element 22 is not used. When the linear element 21 is housed, the lower end of the spiral element 22 is in contact with the fixing fitting 13 and becomes conductive. The linear element 21 functions as a monopole antenna when extended, and the spiral element 22 functions as a helical antenna when stored. The linear element 21 and the spiral element 22 have the same electrical length.

  As shown in FIG. 1, the notch antenna 30 has a flat plate shape and is provided with a notch (notch 31) from its upper end. The notch antenna 30 can be formed by, for example, metal plating on the back side of the back housing 12, but a conductor plate may be arranged on the back side of the back housing 12.

  FIG. 2 is a perspective view showing the vicinity of the feeding portion of the antenna structure. As shown in FIG. 2, the fixture 13 is connected so as to be electrically connected to the inner conductor 41 of the coaxial cable 40. This connection portion becomes a power feeding portion of the notch antenna 30.

  The inner conductor 41 of the coaxial cable 40 is connected to the upper end of the left portion of the notch antenna 30 from the notch 31 so as to be electrically conductive. An outer conductor 42 of the coaxial cable 40 is connected to the right side of the notch 31 of the notch antenna 30 so as to be electrically connected. The outer conductor 42 of the coaxial cable 40 is grounded to a metal substrate or the like in the casing of the mobile phone 10.

  As shown in FIG. 1, the lower end of the coaxial cable 40 is connected to the high-frequency circuit 18 substrate by a coaxial connector 43.

  In the antenna structure of the present invention, two different frequency bands can be used by setting the linear element 21 and the notch antenna 30 in a predetermined dimensional relationship. The dimensional relationship will be described below.

  FIG. 3 is a configuration diagram showing a dimensional relationship between the linear element 21 and the notch antenna 30. The electrical length L1 of the linear element 21 is set to be 1/4 · λ1. Here, λ1 is the wavelength of the center frequency f1 of the first use frequency band, and λ1 = c / f1. The length L2 in the vertical direction of the notch antenna 30 is set to be ¼ · λ1. For this reason, the linear element 21 and the notch antenna 30 constitute an asymmetric dipole antenna of 1/2 · λ1 with respect to the center frequency f1 of the first use frequency band. Using this dipole antenna for f1, communication at the center frequency f1 of the used frequency band can be performed.

  On the other hand, the electrical length L3 of the notch 31 of the notch antenna 30 is set to be ¼ · λ2. Here, λ2 is the wavelength of the center frequency f2 of the second use frequency band, and λ2 = c / f2. For this reason, the notch antenna 30 constitutes a notch antenna 30 having an electrical length of ¼ · λ2 with respect to the center frequency f2 of the used frequency band. Using this notch antenna 30 for f2, communication at the center frequency f2 of the used frequency band can be performed.

  Note that f2 is approximately twice f1, and λ2 = 1/2 · λ1. Therefore, L3 = 1/8 · λ1 and L1 = L2 = 1/2 · λ2. For this reason, the notch antenna 30 for f2 has a very high impedance for the frequency band f1, and is not affected by communication at the center frequency f1 of the used frequency band. Further, the notch antenna 30 for f1 has a very high impedance for the frequency band f2, and is not affected by communication at the center frequency f2 of the used frequency band.

  By forming such an antenna structure, a dipole antenna for the center frequency f1 of the first frequency band to be used and a notch antenna 30 for the second frequency band f2 are formed. No matching circuit is required, the bandwidth of the antenna circuit can be widened, and no mismatch loss occurs.

  Further, since the asymmetrical dipole antenna for f1 is constituted by the linear element 21 and the notch antenna 30, it is not necessary to take a ground in the casing, and a high-frequency current to other metal objects in the casing can be reduced. . Also, better antenna directivity can be obtained compared to a monopole antenna.

  When the telephone user's head is in close contact with the linear element 21 side and the communication is performed in the first frequency band f1, when the f1 dipole antenna is used, only the linear element 21 is used. Compared with the case where the antenna is used as a monopole antenna for f1, a decrease in the radiation efficiency of the antenna can be suppressed, and stable communication becomes possible. Also, when communicating in the second frequency band f2, the notch antenna 30 for f2 can suppress the influence of the human body, and stable communication is possible.

  Next, a second embodiment of the present invention will be described. 4A and 4B are diagrams of the mobile phone 10 to which the antenna structure of the present embodiment is applied. FIG. 4A is a front view, FIG. 4B is a side view, and FIG. 4C is a rear view. This embodiment is different from the first embodiment in that the guide pipe 23 that houses the linear element 21 when not in use has the function of the notch antenna 30.

  A guide pipe (hereinafter, notch pipe 32) having the function of the notch antenna 30 is made of a conductive material. The notch pipe 32 is tubular and is arranged inside the back housing 12 with the vertical direction as the axial direction. Further, the notch pipe 32 is provided with two notches (notches 33 and 34) at two locations on the front side and the back side from the upper end to the lower side. The other points are the same as in the first embodiment.

  Inside the notch pipe 32, the linear element 21 when not in use is housed. As the notch pipe 32, a metal pipe can be used, but the notch pipe 32 may be formed by metal plating on a resin pipe.

  FIG. 5 is a perspective view showing the vicinity of the feeding portion of the antenna structure. As shown in FIG. 2, the fixture 13 is connected so as to be electrically connected to the inner conductor 41 of the coaxial cable 40. Further, as shown in FIG. 5, the upper end of the right side of the notch 33, 34 of the notch pipe 32 is connected so as to be electrically connected to the fixture 13. Further, the outer conductor 42 of the coaxial cable 40 is connected to the left side of the two notches 33 and 34 of the notch pipe 32 so as to be electrically connected.

  FIG. 6 is a configuration diagram showing a dimensional relationship between the linear element 21 and the notch pipe 32. The electrical length L1 of the linear element 21 is set to be 1/4 · λ1. The length L2 in the vertical direction of the notch pipe 32 is set to be 1/4 · λ1. For this reason, the linear element 21 and the notch pipe 32 constitute an asymmetric dipole antenna of 1/2 · λ1 with respect to the center frequency f1 of the first use frequency band. Using this dipole antenna for f1, communication at the center frequency f1 of the used frequency band can be performed.

  On the other hand, the two notches 33 and 34 of the notch pipe 32 have different electrical lengths. The electrical length L3 of one notch 33 is set to be 1/4 · λ2. The electrical length L4 of the other notch 34 is set to be 1/4 · λ2 '. Here, λ2 ′ is the wavelength of the frequency f2 ′ that is slightly higher than the center frequency f2 of the second use frequency band, and λ2 ′ = c / f2 ′. For this reason, the notch pipe 32 constitutes a notch antenna 30 for the center frequency f2 of the second use frequency band, and constitutes a notch antenna 30 for the frequency f2 'slightly higher than the center frequency f2, and with respect to the second frequency band. Can be broadened.

  By forming such an antenna structure, the same effect as that of the first embodiment can be obtained. Further, by providing the guide pipe 23 that accommodates the linear element 21 with the function of the notch antenna 30, the apparatus can be reduced in size.

  Furthermore, since two notches 33 and 34 are provided in the cylindrical conductor in the axial direction to form the notch antenna 30, the second length is obtained by changing the electrical length of the two notches 33 and 34 to resonate with two frequencies. Broadening of the frequency band is possible.

  In the above embodiment, f2 is approximately twice f1, but the present invention is not limited to this, and f2 may be an even multiple of f1. In addition, although the telescopic antenna 20 composed of the linear element 21 and the spiral element 22 is used, a fixed monopole antenna or a helical antenna composed of the linear element 21 or the spiral element 22 alone may be used. Alternatively, the linear element 21 and the spiral element 22 may be combined. Other specific detailed structures can be changed as appropriate.

  Of course, the antenna structure of the present invention can be used not only in a mobile phone but also in other wireless communication devices.

It is a figure which shows the portable telephone to which the antenna structure of this invention is applied, (a) is a front view, (b) is a side view, (c) is a rear view. It is a principal part perspective view of FIG. It is a schematic diagram which shows the dimensional relationship of the antenna structure of this invention. It is a figure which shows the portable telephone to which the antenna structure of this invention is applied, (a) is a front view, (b) is a side view, (c) is a rear view. It is a principal part perspective view of FIG. It is a schematic diagram which shows the dimensional relationship of the antenna structure of this invention.

Explanation of symbols

12 Rear housing 20 Telescopic antenna 21 Linear element 30 Notch antenna 31, 33, 34 Notch 32 Notch pipe

Claims (5)

A first antenna having an electrical length of ¼ of the wavelength λ1 of the center frequency f1 of the first use frequency band and having a first hot part at one end;
A notch extending from one end to the other end, a second hot part at one of the ends divided by the notch , and a ground part at the other, the notch being the center frequency of the second used frequency band an electrical length of a quarter of the wavelength λ2 of f2 Ri Do and a second antenna,
The one end to the other end of the second antenna have an electrical length that is ¼ of the wavelength λ1 of the center frequency f1 of the first use frequency band, and the first antenna and the second antenna are in opposite directions. The asymmetric dipole antenna having an electrical length of ½ of the wavelength λ1 is configured by being arranged so as to extend to and simultaneously fed from a common unbalanced feed line.
An antenna structure characterized by that. The antenna structure according to claim 1 , wherein the center frequency f2 of the second use frequency band is an even multiple of the center frequency f1 of the first use frequency band. The second antenna is a tubular conductor, and has two cuts provided in the axial direction from two places spaced apart in the circumferential direction at one end, and one cut of the center frequency f2 of the second use frequency band. The electrical length is ¼ of the wavelength λ2, and the other notch is ¼ the electrical length of the wavelength λ2 ′ of the frequency f2 ′ different from the center frequency f2 of the second use frequency band. antenna structure according to claim 1 or 2, characterized in that it has the second hot part to one-half by end, the grounding portion at the other by. The antenna structure according to any one of claims 1 to 3 , wherein the second antenna is a tubular conductor, and the first antenna is accommodated therein. The antenna structure according to any one of claims 1 to 4 , wherein the second antenna is formed by metal plating in a casing.

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